XIII 



PHYLUM CHORDATA 



429 



ctsT: 



calcaneal process. The distal row contains three bones the meso- 

 cuneiform, ectocuneiform and cuboid (cub.} ; the ento-cuneiform, 

 which commonly forms the most internal member of this row 

 in other Mammals, is not present as a separate bone. 1 



There are four metatarsals, the hallux or first digit being absent. 

 The proximal end of the second is pro- 

 duced into a process which articulates 

 with the navicular. Each of the digits 

 has three phalanges, which are similar 

 in character to those of the maims. 



The coelome of the Rabbit differs 

 from that of the Pigeon and Lizard in 

 being divided into two parts by a dorso- 

 ventral muscular partition, the diaphragm. 

 The anterior part, or thorax, contains 

 the heart and the roots of the great 

 vessels, the lungs and bronchi, and the 

 posterior part of the oesophagus. The 

 posterior part, or abdomen, contains the 

 stomach and intestine, the liver and 

 pancreas, the spleen, the kidneys, ureters 

 and urinary bladder, and the organs of 

 reproduction. 



Digestive Organs. The teeth (Fig. 

 1019) are lodged in sockets or alveoli in 

 the pre-maxillae, the maxillaa, and the 

 mandible. In the pre-maxillse are situated 

 four teeth- the four upper incisors. Of 

 these the two anterior are very long, 

 curved, chisel-shaped teeth, which are 

 devoid of roots, growing throughout life 

 from persistent pulps. Enamel is pre- 

 sent as a thick layer on the anterior 

 convex surface only, which accounts for 



the bevelled-off character of the distal end the layer of enamel 

 being much harder than the rest, which therefore wears more 

 quickly away at the cutting extremity of the tooth. Along the an- 

 terior surface is a longitudinal groove. The second pair of incisors 

 of the upper jaw are small teeth which are lodged just behind the 

 larger pair. In the lower jaw are two incisors, which correspond 

 in shape with the anterior pair of the upper jaw, the main differ- 

 ence consisting in the absence of the longitudinal groove. The 

 remaining teeth of the upper jaw are lodged in the maxillae 

 Canines, present in most Mammals as a single tooth on each side, 



1 In all probability the homologies of these bones are as follows : astragalus 

 = tibiale -f- intermedium, calcaneum = fibulare, navicular = centrale, ento- cunei- 

 form = 1st distale, meso-cuneiform = 2nd 'distale, ecto-cuneifonn=3rd distale, 

 cuboid = 4th and 5th distalia. 



FIG. 1023. Lepus cuniculus. 



Skeleton of pes. ast. astragalus ; 

 col. calcaneum ; cub. cuboid ; 

 cun. cuneiforms ; nav. navi- 

 cular. 



